Add 2021 Day 22 puzzles

2021/puzzle-22-01.cc

@@ -0,0 +1,84 @@
+#include <array>
+#include <iostream>
+#include <regex>
+#include <string>
+
+using Int = long;
+struct Pos
+{
+  constexpr Pos(Int x, Int y, Int z) : x_(x), y_(y), z_(z) {}
+  [[nodiscard]] constexpr auto x() const noexcept -> Int { return x_; }
+  [[nodiscard]] constexpr auto y() const noexcept -> Int { return y_; }
+  [[nodiscard]] constexpr auto z() const noexcept -> Int { return z_; }
+
+private:
+  Int x_{0};
+  Int y_{0};
+  Int z_{0};
+};
+
+constexpr auto operator==(Pos const& lhs, Pos const& rhs) -> bool
+{
+  return lhs.x() == rhs.x() && lhs.y() == rhs.y() && lhs.z() == rhs.z();
+}
+
+constexpr auto operator<(Pos const& lhs, Pos const& rhs) -> bool
+{
+  return lhs.x() < rhs.x() ||
+         (lhs.x() == rhs.x() && (lhs.y() < rhs.y() || (lhs.y() == rhs.y() && lhs.z() < rhs.z())));
+}
+
+struct State
+{
+  void set(Pos const& from, Pos const& to) { set(from, to, true); }
+  void clear(Pos const& from, Pos const& to) { set(from, to, false); }
+  [[nodiscard]] constexpr auto size() const noexcept
+  {
+    return std::count(nodes_.begin(), nodes_.end(), true);
+  }
+
+private:
+  constexpr static Int min_coord{-50};
+  constexpr static Int max_coord{50};
+  constexpr static Int width{max_coord - min_coord + 1};
+
+  void set(Pos const& from, Pos const& to, bool value)
+  {
+    for (auto x{std::max(min_coord, from.x())}; x <= std::min(max_coord, to.x()); ++x) {
+      for (auto y{std::max(min_coord, from.y())}; y <= std::min(max_coord, to.y()); ++y) {
+        for (auto z{std::max(min_coord, from.z())}; z <= std::min(max_coord, to.z()); ++z) {
+          nodes_[(x - min_coord) * width * width + (y - min_coord) * width + (z - min_coord)] =
+            value;
+        }
+      }
+    }
+  }
+
+  std::array<bool, (width * width * width)> nodes_{false};
+};
+
+auto main() -> int
+{
+  std::regex re{R"((on|off) x=(-?\d+)..(-?\d+),y=(-?\d+)..(-?\d+),z=(-?\d+)..(-?\d+))"};
+  std::string line;
+  State state;
+
+  while (std::getline(std::cin, line) && !line.empty()) {
+    std::smatch m;
+    if (!std::regex_search(line, m, re)) {
+      std::cout << "Unable to match: " << line << '\n';
+      return 1;
+    }
+
+    Pos from{std::stol(m.str(2)), std::stol(m.str(4)), std::stol(m.str(6))};
+    Pos to{std::stol(m.str(3)), std::stol(m.str(5)), std::stol(m.str(7))};
+    if (m.str(1) == "on") {
+      state.set(from, to);
+    }
+    else {
+      state.clear(from, to);
+    }
+  }
+
+  std::cout << "Number lit: " << state.size() << '\n';
+}